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glwidget.cpp Example File
opengl/samplebuffers/glwidget.cpp

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 #include "glwidget.h"
 #include <math.h>

 #ifndef GL_MULTISAMPLE
 #define GL_MULTISAMPLE  0x809D
 #endif

 GLWidget::GLWidget(QWidget *parent)
     : QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
 {
     startTimer(40);
     setWindowTitle(tr("Sample Buffers"));
 }

 void GLWidget::initializeGL()
 {
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     glOrtho(-.5, .5, .5, -.5, -1000, 1000);
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
     glClearColor(1.0f, 1.0f, 1.0f, 1.0f);

     makeObject();
 }

 void GLWidget::resizeGL(int w, int h)
 {
     glViewport(0, 0, w, h);
 }

 void GLWidget::paintGL()
 {
     static float rot = 0.0;
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

     glMatrixMode(GL_MODELVIEW);
     glPushMatrix();
     glEnable(GL_MULTISAMPLE);
     glTranslatef(-0.25f, -0.10f, 0.0f);
     glScalef(0.75f, 1.15f, 0.0f);
     glRotatef(rot, 0.0f, 0.f, 1.0f);
     glCallList(list);
     glPopMatrix();

     glPushMatrix();
     glDisable(GL_MULTISAMPLE);
     glTranslatef(0.25f, -0.10f, 0.0f);
     glScalef(0.75f, 1.15f, 0.0f);
     glRotatef(rot, 0.0f, 0.0f, 1.0f);
     glCallList(list);
     glPopMatrix();

     rot += 0.2f;

     qglColor(Qt::black);
     renderText(-0.35, 0.4, 0.0, "Multisampling enabled");
     renderText(0.15, 0.4, 0.0, "Multisampling disabled");
 }

 void GLWidget::timerEvent(QTimerEvent *)
 {
     update();
 }

 void GLWidget::makeObject()
 {
     QColor trolltechGreen(QColor::fromCmykF(0.40, 0.0, 1.0, 0.0));
     const double Pi = 3.14159265358979323846;
     const int NumSectors = 15;
     GLdouble x1 = +0.06;
     GLdouble y1 = -0.14;
     GLdouble x2 = +0.14;
     GLdouble y2 = -0.06;
     GLdouble x3 = +0.08;
     GLdouble y3 = +0.00;
     GLdouble x4 = +0.30;
     GLdouble y4 = +0.22;

     list = glGenLists(1);
     glNewList(list, GL_COMPILE);
     {
         for (int i = 0; i < NumSectors; ++i) {
             double angle1 = (i * 2 * Pi) / NumSectors;
             GLdouble x5 = 0.30 * sin(angle1);
             GLdouble y5 = 0.30 * cos(angle1);
             GLdouble x6 = 0.20 * sin(angle1);
             GLdouble y6 = 0.20 * cos(angle1);

             double angle2 = ((i + 1) * 2 * Pi) / NumSectors;
             GLdouble x7 = 0.20 * sin(angle2);
             GLdouble y7 = 0.20 * cos(angle2);
             GLdouble x8 = 0.30 * sin(angle2);
             GLdouble y8 = 0.30 * cos(angle2);

             qglColor(trolltechGreen);
             quad(GL_QUADS, x5, y5, x6, y6, x7, y7, x8, y8);
             qglColor(Qt::black);
             quad(GL_LINE_LOOP, x5, y5, x6, y6, x7, y7, x8, y8);
         }

         qglColor(trolltechGreen);
         quad(GL_QUADS, x1, y1, x2, y2, y2, x2, y1, x1);
         quad(GL_QUADS, x3, y3, x4, y4, y4, x4, y3, x3);

         qglColor(Qt::black);
         quad(GL_LINE_LOOP, x1, y1, x2, y2, y2, x2, y1, x1);
         quad(GL_LINE_LOOP, x3, y3, x4, y4, y4, x4, y3, x3);
     }
     glEndList();
 }

 void GLWidget::quad(GLenum primitive, GLdouble x1, GLdouble y1, GLdouble x2, GLdouble y2,
                     GLdouble x3, GLdouble y3, GLdouble x4, GLdouble y4)
 {
     glBegin(primitive);
     {
         glVertex2d(x1, y1);
         glVertex2d(x2, y2);
         glVertex2d(x3, y3);
         glVertex2d(x4, y4);
     }
     glEnd();
 }